/// @author: pengboboer
/// @createDate: 8/18/21
import 'package:intl/intl.dart';

class LunarCalendar {
  //农历年
  int year;

  int month;

  int day;

  bool leap;

  ///中文月名称
  static List<String> chineseNumber = [
    "一",
    "二",
    "三",
    "四",
    "五",
    "六",
    "七",
    "八",
    "九",
    "十",
    "冬",
    "腊"
  ];

  ///中文日期格式
  static DateFormat chineseDateFormat = new DateFormat("yyyy年MM月dd日");

  ///农历数据， 1901 ~ 2100 年之间正确
  static List<int> lunarInfo = [
    0x04bd8,
    0x04ae0,
    0x0a570,
    0x054d5,
    0x0d260,
    0x0d950,
    0x16554,
    0x056a0,
    0x09ad0,
    0x055d2,
    0x04ae0,
    0x0a5b6,
    0x0a4d0,
    0x0d250,
    0x1d255,
    0x0b540,
    0x0d6a0,
    0x0ada2,
    0x095b0,
    0x14977,
    0x04970,
    0x0a4b0,
    0x0b4b5,
    0x06a50,
    0x06d40,
    0x1ab54,
    0x02b60,
    0x09570,
    0x052f2,
    0x04970,
    0x06566,
    0x0d4a0,
    0x0ea50,
    0x06e95,
    0x05ad0,
    0x02b60,
    0x186e3,
    0x092e0,
    0x1c8d7,
    0x0c950,
    0x0d4a0,
    0x1d8a6,
    0x0b550,
    0x056a0,
    0x1a5b4,
    0x025d0,
    0x092d0,
    0x0d2b2,
    0x0a950,
    0x0b557,
    0x06ca0,
    0x0b550,
    0x15355,
    0x04da0,
    0x0a5d0,
    0x14573,
    0x052d0,
    0x0a9a8,
    0x0e950,
    0x06aa0,
    0x0aea6,
    0x0ab50,
    0x04b60,
    0x0aae4,
    0x0a570,
    0x05260,
    0x0f263,
    0x0d950,
    0x05b57,
    0x056a0,
    0x096d0,
    0x04dd5,
    0x04ad0,
    0x0a4d0,
    0x0d4d4,
    0x0d250,
    0x0d558,
    0x0b540,
    0x0b5a0,
    0x195a6,
    0x095b0,
    0x049b0,
    0x0a974,
    0x0a4b0,
    0x0b27a,
    0x06a50,
    0x06d40,
    0x0af46,
    0x0ab60,
    0x09570,
    0x04af5,
    0x04970,
    0x064b0,
    0x074a3,
    0x0ea50,
    0x06b58,
    0x055c0,
    0x0ab60,
    0x096d5,
    0x092e0,
    0x0c960,
    0x0d954,
    0x0d4a0,
    0x0da50,
    0x07552,
    0x056a0,
    0x0abb7,
    0x025d0,
    0x092d0,
    0x0cab5,
    0x0a950,
    0x0b4a0,
    0x0baa4,
    0x0ad50,
    0x055d9,
    0x04ba0,
    0x0a5b0,
    0x15176,
    0x052b0,
    0x0a930,
    0x07954,
    0x06aa0,
    0x0ad50,
    0x05b52,
    0x04b60,
    0x0a6e6,
    0x0a4e0,
    0x0d260,
    0x0ea65,
    0x0d530,
    0x05aa0,
    0x076a3,
    0x096d0,
    0x04bd7,
    0x04ad0,
    0x0a4d0,
    0x1d0b6,
    0x0d250,
    0x0d520,
    0x0dd45,
    0x0b5a0,
    0x056d0,
    0x055b2,
    0x049b0,
    0x0a577,
    0x0a4b0,
    0x0aa50,
    0x1b255,
    0x06d20,
    0x0ada0
  ];

  // 传回农历 y年的总天数
  static int _yearDays(int y) {
    int i,
        sum = 348;
    for (i = 0x8000; i > 0x8; i >>= 1) {
      if ((lunarInfo[y - 1900] & i) != 0) sum += 1;
    }
    return (sum + _leapDays(y));
  }

  // 传回农历 y年闰月的天数
  static int _leapDays(int y) {
    if (_leapMonthM(y) != 0) {
      if ((lunarInfo[y - 1900] & 0x10000) != 0)
        return 30;
      else
        return 29;
    } else
      return 0;
  }

  // 传回农历 y年闰哪个月 1-12 , 没闰传回 0
  static int _leapMonthM(int y) {
    // print('$y');
    return (lunarInfo[y - 1900] & 0xf);
  }

  // 传回农历 y年m月的总天数
  static int _monthDays(int y, int m) {
    if ((lunarInfo[y - 1900] & (0x10000 >> m)) == 0)
      return 29;
    else
      return 30;
  }

  // 传回农历 y年的生肖
  String _animalsYear() {
    final List<String> Animals = [
      "鼠",
      "牛",
      "虎",
      "兔",
      "龙",
      "蛇",
      "马",
      "羊",
      "猴",
      "鸡",
      "狗",
      "猪"
    ];
    return Animals[(year - 4) % 12];
  }

  // 传入 月日的offset 传回干支, 0=甲子
  static String _cyclicalm(int num) {
    final List<String> Gan = ["甲", "乙", "丙", "丁", "戊", "己", "庚", "辛", "壬", "癸"];
    final List<String> Zhi = [
      "子",
      "丑",
      "寅",
      "卯",
      "辰",
      "巳",
      "午",
      "未",
      "申",
      "酉",
      "戌",
      "亥"
    ];
    return (Gan[num % 10] + Zhi[num % 12]);
  }

  // 传入 offset 传回干支, 0=甲子
  String _cyclical() {
    int num = year - 1900 + 36;
    return (_cyclicalm(num));
  }

  static String _getChinaDayString(int day) {
    List<String> chineseTen = ["初", "十", "廿", "卅"];
    int n = day % 10 == 0 ? 9 : day % 10 - 1;
    if (day > 30) return "";
    if (day == 10)
      return "初十";
    else
      return chineseTen[day ~/ 10] + chineseNumber[n];
  }

  String _getChinaMonthString() {
    return chineseNumber[month - 1];
  }

  String toString() {
    return "$year" +
        "年" +
        (leap ? "闰" : "") +
        chineseNumber[month - 1] +
        "月" +
        _getChinaDayString(day);
  }

  ///使用指定日历日期构造一个农历日历
  LunarCalendar(DateTime cal) {
    int yearCyl, monCyl, dayCyl;
    int leapMonth = 0;
    DateTime baseDate;
    try {
      baseDate = chineseDateFormat.parse("1900年1月31日");
    } catch (e) {}

    // 求出和1900年1月31日相差的天数, 注意此处毫秒，除以86400000000
    int offset =
    ((cal.microsecondsSinceEpoch - baseDate.microsecondsSinceEpoch) ~/
        86400000000);
    dayCyl = offset + 40;
    monCyl = 14;

    // 用offset减去每农历年的天数
    // 计算当天是农历第几天
    // i最终结果是农历的年份
    // offset是当年的第几天
    int iYear,
        daysOfYear = 0;
    for (iYear = 1900; iYear < 2050 && offset > 0; iYear++) {
      daysOfYear = _yearDays(iYear);
      offset -= daysOfYear;
      monCyl += 12;
    }
    if (offset < 0) {
      offset += daysOfYear;
      iYear--;
      monCyl -= 12;
    }
    // 农历年份
    year = iYear;

    yearCyl = iYear - 1864;
    leapMonth = _leapMonthM(iYear); // 闰哪个月,1-12
    leap = false;

    // 用当年的天数offset,逐个减去每月（农历）的天数，求出当天是本月的第几天
    int iMonth,
        daysOfMonth = 0;
    for (iMonth = 1; iMonth < 13 && offset > 0; iMonth++) {
      // 闰月
      if (leapMonth > 0 && iMonth == (leapMonth + 1) && !leap) {
        --iMonth;
        leap = true;
        daysOfMonth = _leapDays(year);
      } else
        daysOfMonth = _monthDays(year, iMonth);

      offset -= daysOfMonth;
      // 解除闰月
      if (leap && iMonth == (leapMonth + 1)) leap = false;
      if (!leap) monCyl++;
    }
    // offset为0时，并且刚才计算的月份是闰月，要校正
    if (offset == 0 && leapMonth > 0 && iMonth == leapMonth + 1) {
      if (leap) {
        leap = false;
      } else {
        leap = true;
        --iMonth;
        --monCyl;
      }
    }
    // offset小于0时，也要校正
    if (offset < 0) {
      offset += daysOfMonth;
      --iMonth;
      --monCyl;
    }
    month = iMonth;
    day = offset + 1;
  }

  String getValue() => '${_getChinaMonthString()}月${_getChinaDayString(day)}';

}